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DIMOCK, PA -- Norma Fiorentino’s drinking water well was a time bomb. For weeks, as workers drilled natural gas deposits nearby, stray methane worked into tiny crevasses in the rock, leaking upward into the aquifer and slipping quietly into her well. Then, according to the state’s working theory, a pump turned on in her well house, flicked a spark, and caused a New Year’s morning blast that tossed aside a several-thousand-pound concrete slab.

Afterward state officials found methane, the largest component of natural gas, in her drinking water.

Dimock, the poverty-stricken Susquehana County enclave where Fiorentino lives, is ground zero for drilling the Marcellus Shale, a prized deposit of natural gas touted as one of the most abundant and cleanest alternatives to oil. The drilling here is supposed to be a boon, bringing jobs and millions of dollars in royalties to cash-strapped homeowners.

But a string of documented cases of gas escaping into drinking water – in Pennsylvania and other states – is raising new concerns about the hidden costs of this economic tide and strengthening arguments across the country that drilling can put drinking water at risk.

Near Cleveland, Ohio, a house exploded after gas seeped into its water well. The Ohio Department of Natural Resources blamed a nearby gas well’s faulty cement casing and hydraulic fracturing – a deep-drilling process that shoots millions of gallons of water, sand and chemicals into the ground under explosive pressure – for pushing methane into an aquifer and causing the explosion.

In Dimock several drinking water wells have exploded and nine others were found with so much gas that one homeowner was told to open a window if he planned to take a bath. Dishes showed metallic streaks that couldn’t be washed off and tests also showed high amounts of aluminum and iron, prompting fears that drilling fluids might be contaminating the water along with the gas. In February the Pennsylvania Department of Environmental Protection charged Cabot Oil & Gas with two violations that it says caused the contamination, theorizing that gas leaked from the well casing into fractures underground.

Industry representatives say methane contamination incidents are statistically insignificant, considering that 452,000 wells produced gas in the United States last year. They also point out that methane is common in nature and can leak into water from biological processes like rotting plants.

The industry says its construction technology keeps gas and drilling fluids – including any chemicals used for hydraulic fracturing – safely trapped in layers of steel and concrete. Even if some escapes, they say, thousands of feet of rock make it almost impossible for it to migrate into drinking water aquifers. Those arguments helped the gas drilling industry win rare exemptions from the Safe Drinking Water Act and the Clean Water Act when Congress enacted the 2005 Energy Policy Act.

Now an exhaustive examination of the methane problem in Western Colorado offers a strong scientific repudiation of those arguments. The study matched methane found in dozens of water wells with the same rock layer – a mile and a half underground – where gas companies are drilling. The scientists didn’t say exactly how the gas reached the water, but they indicated with more clarity than ever before that a system of interconnected natural fractures and faults could stretch from deep underground gas layers to the surface.

“It challenges the view that natural gas, and the suite of hydrocarbons that exist around it, is isolated from water supplies by its extreme depth,” said Judy Jordan, the oil and gas liaison for Garfield County, Co. and a hydrogeologist who has worked with DuPont and Pennsylvania’s DEP. “It is highly unlikely that methane would have migrated through natural faults and fractures and coincidentally arrived in domestic wells at the same time oil and gas development started, after having been down there …for over 65 million years.”

Drinking water with methane, the largest component of natural gas, isn’t necessarily harmful. The gas itself isn’t toxic – the Environmental Protection Agency doesn’t even regulate it – and it escapes from water quickly, like bubbles in a soda. But the gas becomes dangerous when it evaporates out of the water and into peoples’ homes, where it can become flammable. It can also suffocate those who breathe it. According to the Agency for Toxic Substances and Disease Registry, as the concentration of gas increases it can cause headaches, then nausea, brain damage and eventually death.

The carefully documented accident in Ohio in December, 2007 offers a step-by-step example of what can happen when drilling goes wrong.

A spark ignited natural gas that had collected in the basement of Richard and Thelma Payne’s home outside Cleveland, shattering windows, blowing doors 20 feet from their hinges and igniting a small fire in a violent flash. Fearing another explosion, firefighters evacuated 19 homes. Investigators determined that somehow gas had seeped into the drinking water aquifer and migrated up through the plumbing.

To reach natural gas, a well bore is drilled through dozens of geologic formations stacked like layers in a cake until it reaches the layer holding gas. In Ohio, gas is produced from almost 3,700 feet, or three-quarters of a mile, below. In Colorado or Pennsylvania, wells can be a mile or two deep – far below drinking water aquifers.

The deep gas layers are under extreme pressure from the weight of the earth and water above. When the drill bit sinks down, the tight seal of each layer is broken and the pressure is released.

To keep the gas and drilling fluids from leaking into the natural environment, drilling companies insert as many as three concentric rings of steel pipes inside the well bore to isolate what flows through them. When the bore passes through sensitive areas – such as drinking water aquifers – cement is pumped into the gap between the rings of pipe to ensure an impenetrable seal.

The investigation into the explosion at the Paynes’ home found that a drilling company working nearby had failed to properly build that protective cement casing. Six weeks before the explosion, the company, Ohio Valley Energy Systems, pumped cement into the well casing but couldn’t fill the gap, evidence that somewhere a crack was allowing the cement to seep out.

Eventually the company shut down the well. But the gas formation had already been punctured, and its contents were trying to escape. The gas collected inside the well until 360 pounds of pressure built against the valve at the top. That was enough, state investigators wrote, to force the gas out of the well bore by any means it could find.

Ohio Valley Energy Systems did not return calls for comment on the state’s findings.

The Garfield County, Colo., report, released in November, was among the first to broadly analyze the ability of contaminants to migrate underground in drilling areas and to find that such contamination was in fact occurring. Using sophisticated scientific techniques, the three-year study examined methane samples from 292 locations and found that methane, as well as wastewater from drilling, was making its way into drinking water not as a result of a single accident but on a broader basis.

As the number of gas wells in the area increased from 200 to 1,300 in this decade, the methane levels in nearby water wells increased too. The study found that natural faults and fractures exist in underground formations in Colorado, and that it may be possible for contaminants to travel through them.

The researchers did not conclude that gas and fluids were migrating directly from the deep pockets of gas the industry was extracting. In fact, they said it was more likely that the gas originated from a weakness somewhere along the well’s structure. But the discovery of so much natural fracturing, combined with fractures made by the drilling process, raises questions about how all those cracks interact with the well bore and whether they could be exacerbating the groundwater contamination, said Geoffrey Thyne, a senior research scientist at the University of Wyoming’s Enhanced Oil Recovery Institute who wrote the report’s summary and conclusion.

The report has been met with cautious silence by the industry and by its regulators.

The Colorado Oil and Gas Association and Encana, the Canadian energy company that drills in the study area, wouldn’t comment either. Both referred questions to Anthony Gorody, a Houston-based geochemist who specializes in oil and gas issues and frequently is employed by the energy industry.

Gorody dismissed the report’s conclusions as “junk science.” He criticized its methodology and said most of the methane in the study area came from decaying matter near the surface, not from the deep gas produced by the energy industry.

“This is so out of whack. There are a handful of wells that have problems. These are rare events,” said Gorody, president of Universal Geosciences Consulting. “They are like plane crashes – the extent tends to be fairly limited. I do not see any pervasive impact.”

When landmen from Cabot Oil & Gas came knocking on doors along the rutted dirt grade of Carter Road in Dimock last year they sold a promise many residents were eager to hear: sign a gas lease and the land might finally pay for itself.

Many of Dimock’s 1,300 residents had fallen on hard times. Approximately one in seven were out of work, and more than a few homes were perched on the precipice of foreclosure.

Cabot offered $25 an acre for the right to drill for five years, plus royalties when the gas started flowing.

“It seemed like God’s provenance,” said Pat Farnelli, whose husband, a farmer, had taken a job as a night chef at a diner on the Interstate to pay one more month’s mortgage. The day Cabot’s man showed up – with a wide-brim hat and a Houston drawl – the Farnellis mistook him for a debt collector. “We really were having a rough time right then – that day. We thought it was salvation. Any ray of hope here is a big deal.”

That was more than a year ago, and since then Cabot – which earned close to a billion dollars in revenue last year – has drilled 20 wells and is producing $58 million worth of gas there annually. In its annual report Cabot bullishly called the Dimock field a once-in-a-lifetime “game changing event” for the company and announced it would drill 63 more wells there next year.

The wealth has begun trickling down to the residents of Dimock. A few will earn more than a half-million dollars this year, and bimonthly checks for $6,000 are not uncommon. Cabot and its contractors also support the local economy by hiring local labor and patronizing hotels and restaurants in nearby towns.

But the water contamination is forcing the people who live there to accept a difficult compromise.

“You have to evaluate which is more important, the money or the water,” said a Dimock resident who declined to be named because he doesn’t want to antagonize Cabot, which he says will pay him more than $600,000 this year for the wells on his property. “The economy is so tough. Suppose you could stop drilling – no one wants Cabot to go away.”

For some, though, the benefits can be easily erased.

Norma Fiorentino, whose well exploded on New Year’s morning, got just $97 in royalties in February. Now a part of her monthly $646 Social Security check goes to buy water. “You can’t buy a good well,” she said.

Down the road, Pat Farnelli spends more than $100 of her monthly food stamp allotment to buy plastic jugs of drinking water. Next door, Ronald Carter, paid $7,000 to install two water treatment systems for his family, then learned they won’t remove the gas.

Cabot has begun voluntarily supplying water to at least five homes in Dimock, a gesture the company says does not mean it has acknowledged fault, said Kenneth Komoroski, Cabot’s spokesman.

Others have yet to get any aid.

“This isn’t something that people should be living with,” said Craig Lobins, the regional oil and gas manager for Pennsylvania’s Department of Environmental Protection. “It’s serious.”

Lobins places responsibility for the contamination squarely on Cabot.

In January the DEP blamed the company for polluting one water well. Then in late February it sent Cabot a list of violations it said led to methane seepage in other area wells. Investigators think the seepage was caused by a weakness in the well casing or an improper cement job, much like what had been reported in Colorado and Ohio. The good news was that they found no evidence that any of the hydraulic fracturing fluids had leaked into well water.

Komoroski, the Cabot spokesman, said it’s too early to conclude the company is responsible for contaminating Dimock’s wells.

“The DEP’s letter was premature,” Komoroski said. “It is possible that Cabot is responsible. It’s possible it is not.”

Cabot Oil & Gas has since pumped cement into the entire length of its well casings in Dimock – a safeguard similar to what has been prescribed in the other states – and believes that measure, which is more extensive than state regulations require, will solve the problem.

Yet Pennsylvania’s DEP sees no need to require full-length cementing at all the state’s wells, because what is happening in Dimock is “an anomaly.”

“Last year we permitted 8,000 wells, and this may be the only incident that occurred,” said the DEP’s Lobins. “You can’t cover every possible scenario that you could encounter out there, so when the regulations are crafted it addresses the ones that will be most protective of 99.9 percent of the wells.”

At the bottom of the hill on Carter Road, Richard Seymour runs a certified natural farm that ships produce across the state. His well is running red and turbid and bubbles with so much gas that he fears he’ll lose that agricultural certification. If there’s a technology, like cementing, that can protect his water, then shouldn’t it be required in every case, he asks?

“We feel pretty alone on this, pretty frustrated,” Seymour said. “I assumed the DEP, EPA, the state – the government – would protect our land. We didn’t know that as a landowner the burden was on us.”

Abrahm Lustgarten is an investigative reporter for ProPublica, an independent, non-profit newsroom that produces journalism in the public interest.